Piston skirt expander



- 1=r L. w. COOMB; I 2,113,912.

PISTON SKIRT EXPANDER Filed Sept. 1, 1934 Jay. 1..

INVENTOR. 22 Leslie WT Coombs 1" 71mg; qmw

HIS ATTORNEYS.

Patented Apr. 12, 1938 UNITED STATES PATENT OFFICE PISTON SKIRT EXPANDER Leslie W; Coombs, Chicago, Ill.

Application September 1, 1934, Serial No. 742,404

. 12 Claims. (01. 1209-12) This invention relates to a piston skirt expander.

It is an object of this invention to provide an improved piston skirt expander which is relatively simple and inexpensive in construction and efficient in use.

Another object of this invention is to provide a piston skirt expander for internalcombustion engine pistons which is characterized by a pair of spring jaws adapted to be engaged with a slot in the piston skirt and a central portion so related to the jaws as to supplement the expansive action thereof on the piston skirt.

Other objects will appear hereinafter.

The invention consists in the novel construction and combination and arrangement of parts to be hereinafter described and claimed.

The invention will best be understood by reference to the accompanying drawing, showing the preferred form of construction and in which:

Fig. 1 is a side elevational view of an internal combustion engine pistonshowing one of the new iexpande'rs in operative position therein; and as position and exerting an expanding force upon the walls of the piston skirt;

Fig. 4 is a sectional view showing a preferred form .of one of the new expanders; and

Fig; 5 is a perspective view of the same.

A preferred form of the new piston skirt ex- 1 pander is illustrated inthe drawing and is generally indicated therein at H]; the same being shown associated with an internal combustion engine piston, generally indicated at I6, and comprising a split skirt I1 having a specially formed dividing slot l8 provided therein; the opposite walls of the slot being correspondingly beveled as at IE to accommodate the jaws I4 of the expander, as will be explained more fully hereinafter.

The new expander I0 is made from suitable, metal, preferably steel, and comprises a resilient body II which includes a substantially U-shaped central portion l2; the arms or sides IQ of this central portion l2 merging into resilient jaw members l3 which are bent back upon the central portion I2 and terminate in .gripping members or fingers l4; it being noted that the new expander, while spanning the slot l8, extends over only a relatively small part of the inner periphery of the piston skirt, as distinguished from the prior art expanders which, in general, extend completely'around the inner periphery of the piston.

By reason of its, own or peculiar construction and its own resiliency, which is imparted to it by the temper and resiliency of the steel from which it is made, the jaws H of the expander are normally spread apart by their own resiliency and that of the central portion i2, substantially into 10 the position of Fig. 4, when the expander is in non-operativeposition. However, in order to insert the expander into operative position,- the gripping fingers or'end portions M of the jaws I3 may be pinched together by means of a suit- 15 able tool, such as a pair of pliers, into the position in which they are shown in Fig. 3, thereby compressing the jaws it against the convex surface of the central portion l2, and in this position the gripping fingers or end portions I l of the jaws l3 may be inserted into the dividing slot iii of the piston skirt l1, and against the beveled walls l5 of the same. When the expander is thus inserted into position in the piston, the jaws i3 and the U-shaped or outwardly bowed centralportion l2 are placed under tension and the jaws i3l4 tend to spread apart in the direction of the oppositely disposed circumferential arrows in Fig. 3 into theirnormal position, as shown in Fig.

4, and in so doing exert an expanding force upon the split skirt I! to urge the same into the desired close contact with the walls of the cylinder in which the piston is arranged.

In addition, the bowed portion 82 is deflected, biased, or displaced radially inwardly by the jaws 35 duringcompression thereof and remains in this biased or resiliently sprung condition while the expander is in operative or assembled position in the piston. I employ the terms deflected,"

biased," displaced, and resiliently sprung as 40 equivalents designating the condition of the portion 82 under the compression of the jaws. of course the equal and opposite reaction arising from this compression is of primary importance in the functioning of my expander. Being un- 5 der such spring tension, the bowed portion l2 tends to return radially outwardly to original position, and being in contact with the jaws It, this radial spring reactive force is transmitted directly to thejaws and serves further to spring the same circumferentially apart. The direction of the expansive forces imparted by the jaws themselves is indicated by the circumferentially disposed arrows in Fig. 3, while the direction of the supplemental radial iorce referred to, resulting in a circumferential spring camming effect, is indicated by the radially disposed arrow in this figure.

While I have illustrated and described the pre-' ferred form of construction for carrying my invention into effect, this is capable of variation and modification, without departing from the spirit of the invention. 1, therefore, do not wish to be limited to the precise details of construction set forth, but desire to avail myself of such variations and modifications as come within the scope of the appended claims.

Having thus described my invention what I claim as new and desire to protect by Letters Patent is:

1. A piston skirt expander comprising a resilient metallic body bent to provide a pair of relatively bulbous side lobes spaced by a rounded central portion having a curvature opposite to that of the lobes; said lobes constituting jaw members disposed one on each side of said central portion; each of said jaw members terminating in a gripping portion and the latter being normally spread apart by the innate resiliency of the said central portions and jaw members; said gripping portions being adapted to be forced together with said jaw members engaging and deflecting said central portion and inserted under tension into a slot provided therefor in the wall of a split piston skirt and when therein tending by reason of the innate resiliency of the said body and. its said central portion and jaw mem-- bers and the tension thus imparted thereto to expand said skirt; said oppositely curved central portion lying closely adjacent the piston skirt and furnishing clearance to avoid interference by the expander with the piston connecting rod in operative position of "the expander on the piston skirt.

2. A piston skirt expander comprising a resilient metallic body, bent to form a pair of opposed substantially circular jaw members connected by a reversely curved central portion; the said jaw members being bent back upon the central portion from opposite ends thereof; each of said jaw members terminating in a gripping member and the latter being normally spread apart by the resiliency of said central portion and jaw members; said gripping members being adapted to be forced together to bring said jaw members in contact with said central portion whereby to deflect the same, said expander being inserted under the tension thus imparted to said central portion and jaw members into the dividing slot provided in the wall of a split piston skirt and when therein tending by reason of the innate resiliency of the said body and its said central portion and jaw members and the tension thus imparted thereto to expand said skirt.

3. A piston skirt expander comprising a resilient metallic body having a curved central portion and side portions curved reversely to the central portion and terminating in resilient jaw members arranged one oneach side of said central portion and bent back circumferentially and radially upon the latter from opposite ends thereof; each of said jaw members terminating in a gripping member and the latter being normally urged apart by the spring action of said jaw members but being adapted to be forced together and inserted into the split or slot ,of a split piston skirt; said expander when thus positioned extending over only a relatively small part of the inner periphery of the piston skirt; said central portion lying closely adjacent the piston skirt in operative position of the expander on the piston skirt.

4. A piston expander comprising a pair of opposed spring jaw members terminating in outwardly disposed piston engaging jaws, and a central spring thrust member, the jaw members being positioned relative to and associated with said central spring thrust member so that compression of the jaw members to piston assembly position relative to each other and to the central spring thrust member brings the jaw members into defleeting engagement with said spring thrust member, thereby producing therein stresses the reaction of which is transmitted through the spring jaw members when the expander is in operative position on a piston.

5. A piston expander formed of spring material and comprising an outwardly bowed central portion having arms which are inwardly bowed and extended into opposed spring jaw members terminating in piston engaging jaws, the jaw members being adapted to be compressed toward each other for assembly in a piston and when compressed to assembly position being supported by and in deflecting engagement with said outwardly bowed central portion and subject to the outward thrust thereof.

6. A piston expander formed of spring material and comprising an outwardly extending central portion, opposed spring jaw members connected to said central portion on either side thereof terminating in piston engaging jaws,,the jaw members being adapted to be compressed toward each other for assembly in a piston and when compressed to assembly position being supported by and in deflecting engagement with said central portion.

'7. An expander for a split skirt piston comprising a .pair of outwardly converging spring jaw members terminating in piston engaging jaws, and a central spring member connected to the inner ends of said jaw members, said jaw members being normally substantially spaced and being placed under expanding stress when collapsed toward each other to position for assembly with a piston, said jaw members in such position engaging and deflecting said central spring member, thereby producing therein bending stresses, the jaw members contacting said central spring member when in their piston engaging position whereby the reaction to said stresses is imparted to said jaw members.

8. An expander for split skirt pistons, comprising a resilient metallic body comprising an outwardly bowed central portion, and a pair of outwardly converging jaw members formed integrally therewith, said body having arms joined to the jaw members, said central portion being connected to said armsby inwardly bowed looplike portions, said jaw members terminating in normally substantially spaced jaws adapted for engagement in the split of a piston skirt when the jaw members are collapsed toward each other under spring stress, said jaw members when so collapsed engaging and deflecting said outwardly bowed central portion from its normal position whereby it is placed under stress, due to such deflection, and augments the resiliency of the jaw members by its tendency to return to its original position. i

9. An expander for a split skirt piston formed of spring material and comprising an outwardly extending spring central portion, and spring jaw members terminating in outwardly diverging piston engaging jaws, said jaw members being normally substantially spaced and subjected to stress when collapsed toward each other for engagement with a piston and when so collapsed being in deflecting engagement with and supported by the said central portion whereby the said central portion and the jaw members mutually coact to expand the skirt of the piston.

10. A piston skirt expander comprising a pair of spring jaw members terminating in piston engaging jaws, said jaw members being movable toward one another to assembly position, and means on said expander intermediate said jaw members to engage said members in assembly position, said members and means being formed for resilient camming engagement and said means tending to expand said members through said camming engagement when the expander is in operative position on a piston.

11. A piston skirt expander comprising a pair tion on a piston.

of spring jaw members terminating in piston engaging jaws, said jaw members being movable toward .one another to assembly position, and means on said expander intermediate said jaw members to engage said members in assembly position, said means tending to expand said members when the expander is in operativeposition on a piston.

112. A piston skirt expander comprising a pair of spring jaw members terminating in piston engaging jaws, said jaw members being movable toward one another to assembly position, and resilient means on said expander intermediate said Jaw members having camming engagement therewith to resist such movement to assembly position, said means tending to expand said members when the expander is in operative posi- LESLIE W. COOMIBS. 

